Collapsible projection screen structure

ABSTRACT

A collapsible projection screen structure comprising an elongate standard, a screen support adjustable along the standard, a screen casing pivotally mounted on the support for movement between upright and horizontal positions, a rolled screen in the casing, an extensible rod on the upper end of the standard for holding the upper end of the screen extended and for holding the upper end of the casing in storage, a stop lug on the standard for limiting downward movement of the support, means on the support normally engageable with the stop lug for defining a storage position of the support on the standard, and means mounting the support on the standard for bypassing the stop lug to selectively lower the screen for viewing.

United States Patent Zinn 1 Feb. 25, 1975 COLLAPSIBLE PROJECTION SCREEN 3,365,155 l/l968 Muller 248/171 STRUCTURE 3,629,910 12/1971 Kirberg 160/24 X [76] Inventor: Robert W. Zinn, Addison, 111. Primary Examiner-J1 Franklin F055 Attorney, Agent, or FirmI-lafgren,'Wegner, Allen, [73] Assignee: Knox Manufacturing Company, Stellman 8; McCord.

ood Dale, Ill1no1s ABSTRACT [22] Filed: May 1973 A collapsible projection screen structure comprising [21] AWL No; 361,854 an elongate standard, a screen support adjustable along the standard, a screen casmg pivotally mounted on the support for movement between upright and Cl 248/125 horizontal positions, a rolled screen in the casing, an it. Cl. extensible rod on the upper end of the standard for Field 0f Search 125, holding the upper end of the screen extended and for 248/327, 333; 351 holding the upper end of the casing in storage, a stop lug on the standard for limiting downward movement References Clted of the support, means on the support normally engage- UNITED STATES PATENTS able with the stop lug for defining a storage position of 1,488,300 3/1924 Thompson 248/125 x the pp on the Standard, and means mounting the 2,361,119 10/1944 Owens 160/24 pp on the rd o bypassing the stop lug to 2,998,001 8/1961 Lofgren et a1. 248/125 X selectively lower the screen for viewing. 3.164.349 1/1965 Armstrong 160/351 UX 15 Claims, 9 Drawing Figures a 1; o t

PATENIED FEB 2 5 I975 SHEET 1 BF 2 COLLAPSIBLE PROJECTION SCREEN STRUCTURE BACKGROUND OF THE INVENTION The invention relates to a collapsible projection screen structure including an elongate standard carrying an adjustable screen support with a screen casing pivotally mounted thereon for movement between an upright storage position parallel to the standard and a horizontal position transverse to the standard where a rolled screen may be extended to a viewing position in an upright plane.

In collapsible screen structures of the type described, it is desirable to provide for vertical adjustment of the screen support on the upright standard and for retention of the support in adjusted positions on the standard. Prior efforts have been devoted to provision of such features as shown, for example, in U.S. Pat. Nos. 1,700,637, 2,335,884, 2,361,ll9 and 3,182,7l4. Generally speaking, the constructions in the aforementioned patents provide for vertical adjustment of a screen support over a wide range of the length of the standard.

Other prior art constructions have included a centering stop on the standard engageable with the screen support for limiting downward movement of the support on the standard at a position where the screen casing will be centrally located in vertical position parallel to the standard for storage, as shown in prior U.S. Pat. Nos. 2,832,405 and 3,164,348, for example. While it is desirable to provide a centering stop on the standard for locating the screen support in proper position for collapse and storage of the structure, it is desirable to permit adjustment of the screen support below the level of the centering stop for purposes of lowering the screen to a viewing position compatible with projection equipment utilized therewith.

SUMMARY OF THE INVENTION It is a general object of the present invention to provide a new and improved collapsible projection screen structure including an upright standard, a screen support vertically adjustable on the standard, a centering stop on the standard normally effective for limiting downward movement of the screen support at a storage position, together with means mounting the support on the standard in a manner permitting manipulation of the support past the centering stop for lowering the screen to an appropriate viewing position.

A more specific object is to provide a new and improved projection screen structure of the type described, including an elongate standard, a screen support adjustable along the standard, a screen casing mounted on the screen support, a rolled screen in the casing, means for holding the support in adjusted positions on the standard, stop means on the standard engageable with the support for limiting downward movement of the support, and means mounting the support on the standard for manipulation past the stop means to selectively lower the support below the stop means.

In a preferred construction illustrated herein, the screen support comprises a U-shaped bracket having spaced upper and lower apertured flanges slidably mounted on the standard, the stop means on the standard comprises a lug engageable with the lower screen support bracket flange, and the aperture in the lower support bracket flange is elongated in a front-to-rear BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a collapsible projection screen structure embodying the principles of the present invention, with the leg assembly in closed position and the screen casing in storage position parallel to the standard;

FIG. 2 is an elevational view of the screen structure with the leg assembly in supporting position, with the screen casing in horizontal position, and with the screen in extended viewing position;

FIG. 3 is a view like FIG. 2 with the screen support lowered past the centering stop to a lowermost position;

FIG. 4 is an enlarged fragmentary elevational view of the upper end of the standard, partly in section, illustrating the means for retaining the extensible rod in adjusted positions in the standard;

FIG. 5 is a transverse sectional view taken at about the line 5-5 of FIG. 6.

FIG. 6 is an enlarged fragmentary transverse sectional view taken at about the line 6-6 of FIG. 2;

FIG. 7 is a fragmentary vertical sectional view taken at about the line 7-7 of FIG. 6, illustrating the screen support in contact with the centering stop on the upright standard;

FIG. 8 is a sectional view taken at about the line 88 of FIG. 7; and

FIG. 9 is a view similar to FIG. 7, but with the screen support manipulatedin a manner to move downwardly past the centering stop on the standard.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT In the embodiment illustrated, and referring particularly to FIGS. 1 and 2, a standard 12 is adapted for support in upright position by a collapsible tripod leg assembly, generally designated 13. The standard carries a screen support member generally designated 14 which is slidably mounted on the standard 12 and provided with a latching member 15 for holding the screen support member 14 in vertically adjusted positions on the standard 12.

The forward face of the screen support member 14 affords a mounting surface to which a conventional screen casing 16 is pivotally mounted. The casing 16 is preferably mounted so that when released from its carrying position parallel to the standard (FIG. 1), it may be pivoted to its operative position perpendicular to the standard, as shown in FIG. 2, where a rolled screen 17 may be extended to a viewing position in an upright plane.

The standard 12 is a tubular member having a telescoping rod 18 slidably received and appropriately guided therein. The telescoping rod 18 is vertically adjustable and held in adjusted positions by a conventional clamping member 21 located near the upper end of the standard 12. The clamping member is preferably biased by a spring member 21a so that it is normally held in clamping position and must be manually released to permit adjustment of the telescoping rod 18. The upper end of the rod 18 carries a bail support 22 from which the free upper end of the projection screen may be hung in a conventional manner. The bail support 22 is provided with a depending lug 23 of a size to fit within a well in the end of the casing 16 to hold the casing 16 in its carrying position parallel to the standard, as shown in FIG. 1.

The leg assembly 13 is provided with an upper collar 28 which slidably embraces the lower end portion of the tubular standard 12 and with a lower collar 30 which is fixedly secured adjacent the lower end of the tubular standard 12. The upper collar 28 is provided with three pairs of angularly spaced ears 31, and the lower collar 30 is likewise provided with three pairs of cars 32 angularly spaced about the lower collar 30 in a manner similar to the spacing of ears 31 on the upper collar 28.

A channel-shaped leg member'33 is swingably secured to each pair of cars 31 by a rivet 341A channelshaped bracing link 35 is similarly pivotally secured at one end to each pair of cars 32 on the lower collar a by rivet 36. The opposite end of each of the bracing links is pivotally secured to an intermediate portion of its associated leg member 33 by a rivet 37.

When the leg assembly 13 is swung toward closed position adjacent the standard 12, the slidable upper collar 28 moves upwardly on the standard 12 (FIG. 1) and the leg members 33 and bracing links 35 swing inwardly about the pivot connections afforded by the rivets 34, 36 and 37. In reverse fashion, when the leg as sembly 13 is moved to extended supporting position, the upper collar 28 slides downwardly upon the standard 12 (FIG. 2) and the leg members 33 and bracing links 35 pivot outwardly.

The details of the leg assembly form no part of the present invention and need not be described completely. If desired, the leg assembly may be similar to that in the aforementioned US. Pat. No. 3,164,348, for example, wherein spring means associated with the leg assembly 13 causes the leg assembly to be yieldably held in. closed position adjacent the standard (FIG. 1), and yieldably held in the outwardly spread supporting position (FIG. 2).

As best illustrated in FIGS. 6-9, the screen support member 14 comprises a U-shaped bracket including spaced upper and lower horizontally directed flanges 50 and 51 which are provided respectively with apertures 52 and 53 receiving the tubular standard 12 so that the screen support bracket 14 is vertically slidably adjustable on the standard. The free ends of the bracket flanges 50 and 51 are connected by a handle member 55 having upper and lower ends respectively connected to the flangesSO and 51.

The latching member 15 is in the form of a plate which has one end pivotally mounted at 56 on the front of the screen support bracket 14. The plate 15 includes an intermediate portion which has an aperture 57' which is enlarged relative to the standard 12 through which the standard 12 passes. The opposite end of the plate 15 is biased downwardly by a coiled compression spring 58 acting between the flange 50 and the plate 15 to urge the latter to an inclined position against the standard 12 so that the edges of the plate adjacent the aperture bite into the standard.

In operation, the weight of the screen casing 16 and the screen 17 on the front of the screen support bracket 14 tend to tilt the upper portion of the bracket forwardly and the lower portion of the bracket rearwardly, as shown in FIG. 7, so that the lower flange 51 is urged into the front of the standard 12 and the upper flange 50 is urged into the rear of the standard 12. Together with such action, the latching plate 15. is biased by spring 58 toward the inclined position illustrated in FIG. 7 where the plate bites into the front and rear surfaces of the standard 12. As a result, the screen support 14 will be held inselected vertically adjusted positions for purposes of locating the lower portion of the screen appropriately for viewing. The support 14 may be vertically adjusted on the standard 12 by grasping the handle 55 in a manner to pivot the latch 15 in a direction to compress the spring 58 such that the latch is released from the standard 12. Under these circumstances, the

screen support 14 may be raised or lowered onthev standard 12.

As seen in FIGS. 7 and 9, the standard 12 includes a stop lug 59 on the front thereof engageable with the lower support flange 51 at a position suitable for centering the screen support 14 on the standard where the casing 16 will be appropriately located for storage when disposed parallel to the standard as illustrated in FIG. 1. In such position, the screen casing is positioned so that the upper end may be held by the projection 23 against pivotal movement relative to the standard. At the same time, the lower end of the casing is slightly elevated above the floor so that the legs 33 support the entire structure. The centering stop 59 is convenient for expediting collapse of the structure, in that it normally functions to define a lower limit against which the screen support 14 should be moved for storage. In order to facilitate retention of the support bracket engaged with stop 59, the upper end of the stop is spaced from the standard 14 as at 59a, and the lower support flange 51 has a lip or lug 51a extending downwardly and positionable in the space 59a.

It sometimes becomes desirable to lower the screen support 14 below the level of the centering stop 59 (FIG. 3) so that the lower portion of the screen in extended operative position may be disposed low enough to accommodate a picture projected from a particular projection apparatus which might not conveniently standard 14 is substantially square in cross section,

while the lower aperture 53 in the support bracket is rectangular, elongated in a front-to-rear direction, so that the bracket may be tilted on the standard from the position shown in FIG. 7 to the positionshown in FIG.

9 where the lower flange 51 is movable past the stop.

at 52a. The recess 52a is rectangularly shaped and of a size to permit the stop lug S9 to pass.

The aperture 57 in the clamp plate is rectangular at four corners to permit the edges of the plate to bite into the standard, but the plate is recessed at the front of the aperture as at 57a. The recess 57a is rectangularly shaped and sized to permit the stop lug 59 to pass.

The construction described, with stop 59, facilitates collapse of the screen structure expeditously by movement of support 14 against stop 59, while also permitting adjustment of the screen support below the stop if that becomes desirable in situations where the image cannot be elevated for projection to the screen when positioned above the stop. As seen in FIG. 3, the support may be lowered to a position adjacent to the collar 28 of the leg assembly 13.

I claim:

1. A projection screen structure, comprising,

a. an elongate standard,

b. a screen support adjustable along an intermediate portion of the standard,

c. a screen casing mounted on the screen support,

d. a rolled screen in the casing,

e. a hanger on the upper end of the standard,

f. means cooperating with the standard and the screen support for holding the support in adjusted positions on the standard,

g. stop means on the standard normally engageable with the support for limiting downward movement of the support at a storage position on the standard, and

h. means mounting the support on the standard for bypassing the stop means to selectively lower the support below the stop means.

2. A projection screen structure as defined in claim I, wherein the screen support comprises a bracket having spaced upper and lower apertured flanges slidably mounted on the standard.

3. A projection screen structure as defined in claim 2, wherein the lower screen support bracket flange aperture is elongated in a front-to-rear direction.

4. A projection screen structure as defined in claim 2, wherein the standard is rectangular in cross section and the screen support bracket flanges have apertures slidably receiving the standard and elongated in a frontto-rear direction to permit movement of the support past the stop.

5. A projection screen structure as defined in claim 2, wherein the stop means comprises a protrusion on the standard, and the lower flange of the support has a stop lug engageable with the protrusion.

6. A projection screen structure as defined in claim 2, wherein the cooperating means for holding the screen support bracket in adjusted positions on the standard comprises a plate pivotally mounted on the bracket and pierced by the standard, spring means resiliently biasing the plate against the standard, and a recess in the plate for passing the stop means on the standard.

7. A collapsible projection screen structure, comprising,

a. an elongate standard,

b. a screen support bracket having spaced flanges with apertures slidably receiving an intermediate portion of the standard for adjustment of the bracket along the standard,

c. a releasable clamp on the bracket engageable with the standard for holding the bracket in adjusted positions on the standard,

(1. a tubular screen casing mounted on the screen sup port for movement between an upright storage position parallel to the standard and a horizontal position transverse to the standard,

e. a rolled screen in the casing extensible from the casing in a upright plane when the casing is horizontally disposed,

f. an extensible rod on the upper end of the standard for holding the upper end of the screen in extended position and for holding the upper end ofthe casing in storage position,

g. releasable clamp means on the standard for holding the rod in adjusted positions,

h. a stop lug on the front of the standard normally engageable with the lower bracket flange to limit downward movement of the bracket at a storage position of thebracket, I

i. the apertures in said bracket flanges being shaped to permit the bracket to be manipulated on the standard to pass the stop lug for movement of the screen to a lower position for viewing, and

j. an aperture in the releasable clamp on the bracket for passing the stop lug.

8.'A collapsible projection screen structure as defined in claim 7 wherein the releasable clamp means on the bracket for holding the bracket on the standard comprises a plate having one end pivotally mounted on the front of the bracket, an intermediate portion having an aperture receiving the standard with a recess for passing the stop lug, an opposite end manually accessible adjacent the handle for manipulation, and spring means resiliently acting between the upper bracket flange and said opposite end of the plate to bias the plate to an inclined position in contact with the standard.

9. A collapsible projection screen structure as defined in claim 7, wherein the standard is substantially square in cross section and the lower aperture in the bracket is rectangularly elongated in a front-to-rear direction, and the upper aperture in the bracket has a recess shaped to pass the stop lug.

10. A collapsible projection screen structure as defined in claim 9, wherein the top of the stop lug is spaced from the standard and the screen support bracket has a projection at the lower end positionable in the space between the standard and the lug.

11. A collapsible projection screen structure, comprising,

a. an elongate standard,

b. a collapsible leg assembly on the lower end of the standard for supporting the standard in upright position,

c. a U-shaped screen support bracket having spaced upper and lower flanges with apertures slidably receiving an intermediate portion of the standard for adjustment of the bracket along the standard,

d. a handle on the back of .the screen support bracket,

e. releasable clamp means on the bracket'engageable with the standard for holding the bracket in adjusted positions on the standard,

f. a tubular screen casing pivotally mounted on the front of the screen support bracket for swinging movement between an upright storage position parallel to the standard and a horizontal position transverse to the standard,

g. a rolled screen in the casing extensible from the casing in an upright plane when the casing is horizontally disposed,

h. an extensible rod slidable in the upper end of the standard having means for holding, the upper end of the screen in extended position and means for holding the upper end of the casing in storage position, V

. releasable clamp means on the standard for holding the rod in adjusted positions,

j. a stop lug on the front of the standard normally engageable with the lower bracket flange on downward movement of the bracket toilimit downward movement of the bracket at a position defining a storage position of the bracket, and

k. the apertures in said bracket flanges being shaped to permit the bracket to be manipulated on the standard to pass the stop lug for movement of the screen to a lower position for viewing.

12. A projection screen structure comprising: an elongate standard adapted to be supported in upright position and having a bail support at its upper end; a screen support member adjustable longitudinally of the standard and having limited transverse movement of the standard; means cooperating with the standard and the screen support for securing the support in adjusted positions longitudinally of the standard; a screen casing pivotally mounted on the screen support for movement between a storage position parallel to the standard and operating position substantially perpendicular to the standard, the casing having a spring urged roller journalled therein; a flexible screen having one marginal edge secured to the roller, the screen being wound around the roller when in closed position and being adapted to be unwound therefrom and suspended from the bail support in exposed viewing position; and cooperating stop portions, one on the'support member and the other on the standard, normally positioned for abutting engagement to limit downward movement of the support member and to position the screen casing for placement in storage position, said limited transverse movement of the support member moving said one stop portion transversely of the standard to bypass said other stop portion so as to selectively lower the support below said other stop portion to expose a portion of the screen in viewing position below said other stop portion;

13. A projection screen structure as specified in claim 12 in which the one stop portion is normally urged toward the standard.

14. A projection screen structure as specified in claim 12 in which the support member has upper and lower flanges each slidably embracing the standard and being joined by a mounting portion for the, screen casing, one flange having a cut-out portion to bypass the other stop portion and the other flange having a relieved portion to permit limited transverse movement of the support member to enable the one stop portion to bypass the other stop portion during longitudinal adjustment of the support member.

15. A projection screen structure as specified in claim 12 in which the support member has upper and lower flanges each slidably embracing the standard, the 1 forward flange portions being joined by a mounting portion for the screen casing, the upper flange having a cut-out portion adjacent the forward side of the standard to bypass the other stop portion and the lower flange having a relieved portion to permit limited forward transverse movement of the lower flange to enable the one stop portion to bypass the other stop portion during longitudinal adjustment of the support member. 

1. A projection screen structure, comprising, a. an elongate standard, b. a screen support adjustable along an intermediate portion of the standard, c. a screen casing mounted on the screen support, d. a rolled screen in the casing, e. a hanger on the upper end of the standard, f. means cooperating with the standard and the screen support for holding the support in adjusted poSitions on the standard, g. stop means on the standard normally engageable with the support for limiting downward movement of the support at a storage position on the standard, and h. means mounting the support on the standard for bypassing the stop means to selectively lower the support below the stop means.
 2. A projection screen structure as defined in claim 1, wherein the screen support comprises a bracket having spaced upper and lower apertured flanges slidably mounted on the standard.
 3. A projection screen structure as defined in claim 2, wherein the lower screen support bracket flange aperture is elongated in a front-to-rear direction.
 4. A projection screen structure as defined in claim 2, wherein the standard is rectangular in cross section and the screen support bracket flanges have apertures slidably receiving the standard and elongated in a front-to-rear direction to permit movement of the support past the stop.
 5. A projection screen structure as defined in claim 2, wherein the stop means comprises a protrusion on the standard, and the lower flange of the support has a stop lug engageable with the protrusion.
 6. A projection screen structure as defined in claim 2, wherein the cooperating means for holding the screen support bracket in adjusted positions on the standard comprises a plate pivotally mounted on the bracket and pierced by the standard, spring means resiliently biasing the plate against the standard, and a recess in the plate for passing the stop means on the standard.
 7. A collapsible projection screen structure, comprising, a. an elongate standard, b. a screen support bracket having spaced flanges with apertures slidably receiving an intermediate portion of the standard for adjustment of the bracket along the standard, c. a releasable clamp on the bracket engageable with the standard for holding the bracket in adjusted positions on the standard, d. a tubular screen casing mounted on the screen support for movement between an upright storage position parallel to the standard and a horizontal position transverse to the standard, e. a rolled screen in the casing extensible from the casing in a upright plane when the casing is horizontally disposed, f. an extensible rod on the upper end of the standard for holding the upper end of the screen in extended position and for holding the upper end of the casing in storage position, g. releasable clamp means on the standard for holding the rod in adjusted positions, h. a stop lug on the front of the standard normally engageable with the lower bracket flange to limit downward movement of the bracket at a storage position of the bracket, i. the apertures in said bracket flanges being shaped to permit the bracket to be manipulated on the standard to pass the stop lug for movement of the screen to a lower position for viewing, and j. an aperture in the releasable clamp on the bracket for passing the stop lug.
 8. A collapsible projection screen structure as defined in claim 7 wherein the releasable clamp means on the bracket for holding the bracket on the standard comprises a plate having one end pivotally mounted on the front of the bracket, an intermediate portion having an aperture receiving the standard with a recess for passing the stop lug, an opposite end manually accessible adjacent the handle for manipulation, and spring means resiliently acting between the upper bracket flange and said opposite end of the plate to bias the plate to an inclined position in contact with the standard.
 9. A collapsible projection screen structure as defined in claim 7, wherein the standard is substantially square in cross section and the lower aperture in the bracket is rectangularly elongated in a front-to-rear direction, and the upper aperture in the bracket has a recess shaped to pass the stop lug.
 10. A collapsible projection screen structure as defined in claim 9, wherein the top of the stop lug is spaced from the standard and the scrEen support bracket has a projection at the lower end positionable in the space between the standard and the lug.
 11. A collapsible projection screen structure, comprising, a. an elongate standard, b. a collapsible leg assembly on the lower end of the standard for supporting the standard in upright position, c. a U-shaped screen support bracket having spaced upper and lower flanges with apertures slidably receiving an intermediate portion of the standard for adjustment of the bracket along the standard, d. a handle on the back of the screen support bracket, e. releasable clamp means on the bracket engageable with the standard for holding the bracket in adjusted positions on the standard, f. a tubular screen casing pivotally mounted on the front of the screen support bracket for swinging movement between an upright storage position parallel to the standard and a horizontal position transverse to the standard, g. a rolled screen in the casing extensible from the casing in an upright plane when the casing is horizontally disposed, h. an extensible rod slidable in the upper end of the standard having means for holding the upper end of the screen in extended position and means for holding the upper end of the casing in storage position, i. releasable clamp means on the standard for holding the rod in adjusted positions, j. a stop lug on the front of the standard normally engageable with the lower bracket flange on downward movement of the bracket to limit downward movement of the bracket at a position defining a storage position of the bracket, and k. the apertures in said bracket flanges being shaped to permit the bracket to be manipulated on the standard to pass the stop lug for movement of the screen to a lower position for viewing.
 12. A projection screen structure comprising: an elongate standard adapted to be supported in upright position and having a bail support at its upper end; a screen support member adjustable longitudinally of the standard and having limited transverse movement of the standard; means cooperating with the standard and the screen support for securing the support in adjusted positions longitudinally of the standard; a screen casing pivotally mounted on the screen support for movement between a storage position parallel to the standard and operating position substantially perpendicular to the standard, the casing having a spring-urged roller journalled therein; a flexible screen having one marginal edge secured to the roller, the screen being wound around the roller when in closed position and being adapted to be unwound therefrom and suspended from the bail support in exposed viewing position; and cooperating stop portions, one on the support member and the other on the standard, normally positioned for abutting engagement to limit downward movement of the support member and to position the screen casing for placement in storage position, said limited transverse movement of the support member moving said one stop portion transversely of the standard to bypass said other stop portion so as to selectively lower the support below said other stop portion to expose a portion of the screen in viewing position below said other stop portion.
 13. A projection screen structure as specified in claim 12 in which the one stop portion is normally urged toward the standard.
 14. A projection screen structure as specified in claim 12 in which the support member has upper and lower flanges each slidably embracing the standard and being joined by a mounting portion for the screen casing, one flange having a cut-out portion to bypass the other stop portion and the other flange having a relieved portion to permit limited transverse movement of the support member to enable the one stop portion to bypass the other stop portion during longitudinal adjustment of the support member.
 15. A projection screen structure as specified in claim 12 in which the support member has upper and lower flanges each slidablY embracing the standard, the forward flange portions being joined by a mounting portion for the screen casing, the upper flange having a cut-out portion adjacent the forward side of the standard to bypass the other stop portion and the lower flange having a relieved portion to permit limited forward transverse movement of the lower flange to enable the one stop portion to bypass the other stop portion during longitudinal adjustment of the support member. 